[fedora-virt] stop ksm on the fly?

[Tom Horsley]

On Sat, 19 Dec 2009 15:47:36 +0200
Dan Kenigsberg wrote:

> Perfectly safe - as long as you have enough memory. Otherwise, the VMs
> might start swapping to disk which may be even worse than what you have
> now.

Yea, once the install I was doing finished, I went ahead and tried
it and nothing drastic happened (and I got some cycles back).

> Now since there's still to be desired in ksmtune, would you give some
> info about your system (total ram, number and sizes of VMs, and `more
> /sys/kernel/mm/ksm/*`)

The smolt profile is:

 http://www.smolts.org/client/show/pub_fde3037c-3bfd-4a28-9f73-601d559b6567

4 dual core opterons (total of 8 processors), 8 gig of memory, a gazillion
different VMs defines for lots of different linux distros and versions
(we use it for testing our software under a all those versions), so it
is highly unlikely that any two machines would have many similar pages.
Each VM is configured with 1 gig of virtual memory, and my testbeds never
have more than 7 running at the same time (which leaves plenty of
memory for the host as well as each vm).

Here's the ksm files (but this is long after I already disabled ksm, so
I don't know if these are meaningful anymore):

[root at xen ~]# more /sys/kernel/mm/ksm/*
::::::::::::::
/sys/kernel/mm/ksm/full_scans
::::::::::::::
16085
::::::::::::::
/sys/kernel/mm/ksm/max_kernel_pages
::::::::::::::
1024201
::::::::::::::
/sys/kernel/mm/ksm/pages_shared
::::::::::::::
44390
::::::::::::::
/sys/kernel/mm/ksm/pages_sharing
::::::::::::::
90333
::::::::::::::
/sys/kernel/mm/ksm/pages_to_scan
::::::::::::::
1250
::::::::::::::
/sys/kernel/mm/ksm/pages_unshared
::::::::::::::
815693
::::::::::::::
/sys/kernel/mm/ksm/pages_volatile
::::::::::::::
72635
::::::::::::::
/sys/kernel/mm/ksm/run
::::::::::::::
0
::::::::::::::
/sys/kernel/mm/ksm/sleep_millisecs
::::::::::::::
20